If the US reduces its requirements so that the only biometric required is an image - effectively, an electronic, digitised, photograph. This was already envisaged by 2003 ICAO regulations.
In this case, there is no need for the Passport Office to open up the 70 or so new regional offices (at the moment it only has 6 or 7), nor is there any need for it to spend a fortune on the IT systems required for iris scans, fingerprints etc.
If so, this destroys the argument that most of the costs involved in the ID card scheme have to be spent because of the need to produce passports acceptable to the Americans. The huge cost of these systems would be purely and simply attributable to the ID card scheme.